Fears have been raised by security personnel over the number of "potentially dangerous" people MI5 and the police currently have to monitor because they were released on court bail against security advice

Fears have been raised by security personnel over the number of "potentially dangerous" people MI5 and the police currently have to monitor because they were released on court bail against security advice.

We are the first media outlet in the world to be invited to report from inside MI5's Northern Ireland headquarters.

With the threat from dissident republican terrorists here considered 'severe' and recently upgraded to 'substantial' across the rest of the UK, the work of MI5 has become even more vital.

And now security sources have said there is growing concern over the continued granting of court bail to terror suspects.

Some of the province's terror suspects have been released on bail in recent months due to lengthy delays in processing terrorism cases through the courts.

When considering bail applications each case has to be assessed on its individual merits.

Some of the main factors taken into consideration by the court are if there is a risk of further offending, a risk of interference with witnesses, whether the accused is likely to turn up, and whether there is any risk to public order if the person is released.

Undue delay in the court process is another factor considered for bail applications.

Security sources have told the Belfast Telegraph they have become increasingly frustrated by the number of suspects being released by judges.

"It's frustrating when they get out on bail on different levels. People charged with similar offences would not be given bail elsewhere in the UK," a source said.

The source added: "Where people facing such charges are released - even with conditions - there is a risk they will get involved in some level of activity. It does create pressures for the security services whose work on other investigations doesn't just stop."

MI5 has finite resources and needs to prioritise who is monitored based on the threat they may pose.

The length of time it can take cases to progress through the court system in Northern Ireland is also believed to cause concern to the authorities.

One case has been in the system several years, while similar cases in Britain take around a year.

Meanwhile, the overall head of MI5, director general Andrew Parker, told the Belfast Telegraph that the majority of terrorist attacks have been thwarted by the agency and police.

"Working with the PSNI and others it's MI5's job to keep Northern Ireland safe. Together we have had many successes and we have been able to help stop the majority of terrorist attacks before they come to fruition," said Mr Parker in a statement.

"Our success defending the freedoms we all enjoy depends on maintaining the trust of the public we serve.

"Misperceptions and misrepresentations of the past mean that trust is lower in Northern Ireland than in the rest of the UK."

Mr Parker added: "We will be able to do our jobs better if we have the support of the whole community. So - whilst there are limits to what we can say about how we stop attacks in order that we can keep doing it - I want people in Northern Ireland to see we are a modern, inclusive organisation operating to the highest ethical standards within a clear legal framework, and subject to proper independent scrutiny."